Electric cable.



No. 665,666. Patnted Jan. 6, 19m. 6. K. GRAY.

.ELEGTRIG CABLE.

A limi'cn' filed m 23. 1900.)

(No Model.)

' film/awa W UNITED STATES PATENT OFFICE.

ROBERT KAYE GRAY, OF LONDON, ENGLAND.

ELECTRIC CABLE.

SPECIFICATION forming part Of Letters Patent NO. 665,636, dated. January 8, 1901.

Application filed May 23, 1900. Serial No. 17,700. (No model.)

To all whom it Wtcty concern:

Be it known that I, ROBERT KAYE GRAY, a subject of the Queen of England, residing at London, England, have invented certain new and useful Improvements in or Relating to Electric Cables, (for which application for patent has been made in Great Britain under No. 5,356, dated March 21, 1900,) of which the following is a specification.

This invention relates to improvements in electric cables, and has special reference to cables which are insulated with successive layers of, say, gutta-percha and some plastic or semiplastic insulating compound.

The primary object of the invention is to obviate the tendency of the plastic or semiplastic coating to flow or become displaced relatively to the central core.

In electric cables according to this invention the conductor, which maybe of any convenient form, solid or stranded, is first covered with a coating of gutta-percha or similar insulating material which when in position retains its shape fairly well. The application of the gutta-percha is accomplished in such a Way-by molding or pressing, for instance-that longitudinal ribs or projections are formed upon the outside of the coating. Around the gutta-percha coating is placed a covering of a compoundsuch, for example, as one of the various well-known rubber compounds-which closely envelops the ribbed circumference of the gutta-percha coating. Outside this compound coating another coverin g of gutta-percha is preferably provided, and outside this, again, may be braiding, sheathing, or any of the ordinary outside coverings used in electric cables. In some cases the outer retaining-coating of gutta-percha is dispensed With, a retaining covering of tape or other suitable material being employed instead.

In the accompanying drawings, Figure l is a side elevation of one construction of electric cable according to this invention, portions of the various insulating-layers being removed for. the sake of clearness; and Fig. 2 is a transverse section on the line 2 2 of Fig. 1.

Like letters indicate like parts throughout the drawings.

Around a central conductor A,which in this instance is formed of stranded wires, is a coating B of gutta-percha or other insulating material which after its application to the conductor retains its shape fairly well. Four longitudinal ribs B are formed upon the circumference of the insulating-coatingB in order to prevent the succeeding insulating-covering O, which is of a plastic or semiplastic nature, from becoming displaced relatively to the cen tral core A. Around the insulating-covering O is an outer coating of gutta-percha D.

In some cases it may be desired to have another insulating-layer of plastic or semiplastic material outside the covering D. In these circumstances the coating D would be provided with longitudinal ribs or projections somewhat similar to those upon the inner coating B. Any desired number of alternate layers of a fairly hard material, such as guttapercha,and a plastic or semiplastic com pound may be employed. It is preferred in all cases to make the innermost of such layers of the harder material; but the outermost layer may, if desired, be of tape or other material acting as a retaining-covering. The ribs or projections may be of any convenient form and may be variously disposed around the circumference of the insulating-coating.

Cables according to this invention with more than one conductor may have each conductor provided with a ribbed insulation of fairly hard material and an outer covering of plastic insulation, the various conductors, with their insulating -coverings, being then inclosed in a common covering of the harder insulating material.

What I claim as my invention, and desire to secure by Letters Patent, is-

1. In an electric cable the combination of a conductor, an insulating-coating of plastic or semiplastic material and means interposed between the conductor andthe coating to prevent the flow or displacementof such coating.

2. In an electric cable the combination of a conductor, an insulating-coating around the conductor, longitudinal ribs upon the coating and another insulating-coating of plastic or semiplastic material which is prevented from displacement by means of the ribs substantially as set forth.

3. In an electric cable the combination of a conductor, alternate layers of hard and plastic or semiplastic insulating material around around the plastic or sexniplastic covering sub [0 the conductor and longitudinal ribs upon the stantially as set forth. hard material substantially as set forth. In testimony whereof I have signed my 4:. In an electric cable the combination of a name to this specification in the presence of 5 conductor, a coating of gutta-percha around two subscribing Witnesses.

the conductor, longitudinal ribs upon the ROBERT KAYE GRAY. gutta-percha coating, a covering of plastic or Witnesses: semiplastic insulating material around the JOSH. D. WATTS,

gutta-percha coating, and a retaining-coating ARTHUR OARRIOK. 

